Method and apparatus for detecting transmitters for a white space device

ABSTRACT

The invention relates to a wireless home gateway apparatus and methods of wirelessly delivering audio and/or video programs between a home gateway and a client and mitigating interference thereon. Specifically, the present invention relates to transmitting an audio/video program on two white space channels and alternately stopping transmission on one of said channels to search for external transmissions on the white space channel. The present invention permits the wireless home gateway to continuously transmit an audio/video program to a client while periodically searching for transmitters on each of the white space channels.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit, under 35 U.S.C. §365 ofInternational Application PCT/US2010/000100, filed Jan. 15, 2010, whichwas published in accordance with PCT Article 21(2) on Jun. 23, 2011 inEnglish and which claims the benefit of U.S. provisional patentapplication No. 61/286,227, filed Dec. 14, 2009.

FIELD OF THE INVENTION

The invention relates to a wireless home gateway apparatus and methodsof wirelessly delivering audio and/or video programs between a homegateway and a client device. Specifically, the invention relates tointerference mitigation by facilitating the changing of white spacetransmission frequencies in response to a user experience.

BACKGROUND OF THE INVENTION

The present invention generally relates to an apparatus and methods forpresenting audio and video content on a plurality of display devicesusing a single home gateway server. The apparatus and methods also allowthe user of at least one of the display devices to signal the gatewayhome server to change transmission frequencies in response to a userrequest.

This section is intended to introduce the reader to various aspects ofart, which may be related to various aspects of the present inventionthat are described below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present invention.Accordingly, it should be understood that these statements are to beread in this light, and not as admissions of prior art.

The white space spectrum comprises unused frequency bands primarily inthe FM and television signal bandwidths. New government regulations haveenabled the use of this unused bandwidth for use by wireless interfaceswithin the home. Previously, computers and set-top boxes were requiredto access content through hard wired transmission means, such as coaxialcable or Ethernet cable, or were restricted to transmitting on dedicatedfrequencies often shared by wireless networks and cordless telephoneswhere those frequencies were outside of the FM and television bands.

Devices that take advantage of white space, called white space devices(WSD) are designed to detect the presence of existing signals, such asTV stations and other wireless users, and to then avoid the use of thesechannels. WSD then transmit and receive information on the unusedportions of the spectrum, or the white space. Detection can includesensing signals within the spectrum, or using GPS and receiversdatabases of known transmitters within the area. The databases can beupdated via the internet, known transmitters, or by the WSD themselves.

In operation, the WSD may search the allowable spectrum for a frequencyband not in use. The WSD will then transmit the channel to be monitoredto the display device or a device which controls the channel selectionof the display device. The display device then tunes the channel asindicated by the WSD so that the viewer can view the informationtransmitted by using a standard tuner installed in the device orassociated with the device.

A problem with traditional WSD operation is that new transmitters maycome online after the WSD has begun transmitting on the white spacechannel and the WSD may then interfere with the new transmitter. Amethod and apparatus for detecting new transmitters would be desirableto overcome this problem.

SUMMARY OF THE INVENTION

In order to solve the problems described above, the present inventionconcerns an apparatus and associated methods for receiving video contentand transmitting it to display devices over white space channels orunused channels within a geographic location. This and other aspects ofthe invention will be described in detail with reference to theaccompanying Drawings.

Generally, the present invention defines an apparatus comprising a firsttransmitter for transmitting an audio/video program at a firstfrequency, a second transmitter for transmitting the audio/video programat a second frequency; and a detector for detecting an externaltransmitter at the first frequency and the second frequency, wherein thefirst transmitter stops transmitting the audio/video program during afirst time period during which time the second transmitter istransmitting, wherein the second transmitter stops transmitting theaudio/video program during a second time period during which time thefirst transmitter is transmitting; and wherein the detector attempts todetect the external transmitter during the first time period at thefirst frequency and during the second time period at the secondfrequency.

In accordance with another aspect of the invention, comprises a methodcomprising the steps of transmitting a audio/video program at a firstfrequency, transmitting the audio/video program at a second frequency,stopping transmission of the audio/video program at the first frequency,detecting an external transmission at the first frequency, resuming thetransmission of the audio/video program at the first frequency, stoppingtransmission of the audio/video program at the second frequency,detecting the external transmission at the second frequency, andresuming the transmission of the audio/video program at the secondfrequency.

These and other aspects of the invention will be explained withreference to a preferred embodiment of the invention show in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent, and theinvention will be better understood, by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a block diagram of a white space home gateway interface systemembodying aspects of the present invention;

FIG. 2 is a block diagram of a white space home gateway interface systemhaving multiple television receivers and multiple remote controlsembodying aspects of the present invention;

FIG. 3 is a flow chart of an exemplary method of initializing a whitespace home gateway interface according to the present invention;

FIG. 4 is a flow chart of an exemplary method of mitigating interferencein a home gateway interface according to the present invention;

FIG. 5 is a block diagram of a dual frequency white space systemembodying aspects of the present invention;

FIG. 6. depicts the parallel transmission of data over a dual frequencywhite space system embodying aspects of the present invention.

The exemplifications set out herein illustrate preferred embodiments ofthe invention, and such exemplifications are not to be construed aslimiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE DRAWINGS

As described herein, the present invention provides a display serverapparatus and associated methods for receiving video content andproviding it to multiple display devices. Such a display server mayinclude advanced features, including distribution of video and/or audioover unused radio frequency (RF) channels, commonly referred to as whitespace channels, interaction with RF and infrared (IR) remote controls,and advanced user interface applications to display content available toremote video display units.

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

Turning to FIG. 1, a block diagram of a white space home gatewayinterface system embodying aspects of the present invention is shown.The white space home gateway interface 100 system of FIG. 1 comprises ahome gateway interface 110, a first personal computer 120, a secondpersonal computer 130, a display device 140, a set top box 150, a remotecontrol 160 and a network router 170.

The home gateway interface 110 is a device utilized to distribute audioand video programs to user devices over unused RF frequencies. The homegateway interface 110 comprises at least one terrestrial white spacemodulator which facilitates the broadcast of an audio or video programover the unused RF frequency. The home gateway interface 110 isoperative to sense the RF spectrum and find unused RF frequencies,commonly called white space channels. The home gateway interface 110then modulates a requested audio or video program using the terrestrialwhite space modulator to the unused RF frequency. The home gatewayinterface 110 then transmits this modulated signal via an antenna. Thehome gateway interface 110 is further operative to transmit dataindicating the RF frequency to a receiving device or a remote control160, such that the receiving device, such as a display device 140 or aset top box 150 with signal processing capabilities or a remote control160, capable of controlling these devices, is operative to tune thewhite space channel to receive the program. Often the receiving devicehas no transmission capabilities, so therefore the home gatewayinterface must supply the all the necessary data to facilitate the useof the device.

The home gateway interface 110 can be capable of receiving audio videocontent through any number of methods. The home gateway interface may beable to access content such as music or video files stored on a personalcomputer 120, 130. The home gateway interface 110 may be operative tocontrol the personal computer via RF transmission wherein the personalcomputer 120, 130 comprises an antenna capable of receiving thetransmission. The home gateway interface 110 may be further operative tocontrol the personal computer via the network router over an hardwiredconnection, such as Ethernet wire, or over a wireless connection, suchas the IEEE 802.11 set of standards for carrying out wireless local areanetwork (WLAN) computer communication in the 2.4, 3.6 and 5 GHzfrequency bands. Content can be transmitted to the home gatewayinterface 110 from the personal computer 120, 130 via the sametransmission paths or different transmission paths. For example, thepersonal computer 120, 130 may receive commands from the home gatewayinterface 110 via a direct RF link, and the requested contenttransmitted to from the personal computer 120, 130 to the home gatewayinterface 110 via a hardwired home network. The home gateway interface110 may further receive content via direct connection to a cabletelevision system, fiber optic network, satellite antenna, or via anantenna capable of receiving ATSC television broadcasts or radio signalsin the FM band. The home gateway interface 110 may receive content viaany manner of transmission, or the content may be stored in memory or ona hard drive on the home gateway interface itself. The manner ofreceiving the content is not an essential element in the operation ofthe present invention and the present invention will be operative in asimilar manner using any method of content access.

The whitespace channels can further be used as a high rate datatransmission path to a remote system with a personal computer 130 wherethe personal computer 130 is either stand alone, or integrated in thedisplay device 140 for example. This transmission path could be used tostream content wirelessly without the need for contention of the channeland the MAC overhead encountered in a WLAN. The link could be forstreaming video, or data could be conveyed using the ATSC A-90 standard.The personal computer 130 could be configured with an ATSC receiver, andthe home gateway interface 110 could transmit streaming data to thecomputer's ATSC receiver. This could also be accomplished using a cableinterface using DVB-C, DVB-C2, QAM or other cable standard modulations(FIG. 6). Configuration of the computer interface is easily facilitatedsince there is a parallel LAN interface (Wired or wireless) to thecomputer through which configuration information can be conveyed.

The home gateway interface 110 may be the central point of access forall content in the home. The home network will provide access to userprovided content, the ISP will provide access to internet content,subscription content and other high value content can be provided overother satellite, cable, DSL or Fiber interfaces. Menus accessible by theremote will allow the user access to the wide variety of content. Someservice providers may have program guides to help with the selection ofcontent, also accessible via the remote control.

In an exemplary embodiment, the display device 140 can be a standardATSC television receiver, incapable of communicating with the homegateway interface 140. Thus a key component of a system according tothis embodiment is the remote control 160, which becomes a simpleunifying device in the system, combined with a terrestrial TV whitespace modulator in the home gateway interface 110, which provides thewireless path to the display device. In this configuration, the homegateway interface 110 tells the remote control 160 via an RF signal,either on the white space frequency or another dedicated RF frequencysuch as WiFi, ZigBee or the like which white space channel it will useto reach the television receiver in the home. The remote control 160 isfurther operative to send a control signal to the display device 140 ortelevision signal receiver to enable the display device 140 ortelevision signal receiver to tune to the correct white space channel.

The remote control 160 can be operative to control the display device140, a set top box 150 and the home gateway interface 110. The remotecontrol 160 can transmit these commands by RF transmission or IR controlsignals. The remote control 160 can be further operative to control thehome gateway interface 110 to bring up the home gateway interface 110screen on the display device and permitting a user to select fromavailable audio video content, or permitting a user to access theInternet via the home gateway interface 110. The remote control 160 cancontrol the display device 140 by permitting the user to control theaudio volume, picture characteristics, such as brightness, contrast andthe like.

The remote control 160 ties in to the home gateway with a wirelessinterface. Since the data rates are low from the remote to the gateway,a proprietary interface could be used to minimize power consumption inthe remote. However, the remote could access the home gateway usingWiFi, for a standard based implementation.

The home gateway interface 110 will need to sense the TV channels tofind a white space channel to make the link to the television receiver.Alternately, location based methods can be used to identify the freechannel when the gateway is in a fixed location. The home gatewayinterface 110 could use geographical coordinates to see which TVchannels are occupied by incumbent licensed signals and which TVchannels are available for white space usage.

If the user has poor reception on a given whitespace channel, the remotecontrol 160 will provide a button to change the RF channel. This willchange the physical characteristics of the multipath at the receiver,and may improve the reception from the home gateway interface 110 to thetelevision receiver. A simple antenna could be used in the receiver, andthe ability to change RF channels would benefit the link from thegateway to the television receiver.

Turning to FIG. 2, a block diagram of a white space home gatewayinterface system 200 having multiple television receivers and multipleremote controls embodying aspects of the present invention is shown. Thesystem 200 shown in FIG. 2 is similar to the system of FIG. 1 modifiedto include more television signal receivers 230, 250, 270 and multipleremote controls 240 260, 280. The television signal receivers 230, 250,270 could be display devices, or set top boxes capable of receiving RFsignals from the home gateway device 210. A single home gateway devicecould support multiple television signal receivers 230, 250, 270, sincethere could multiple white space channels available. This size of thesystem of FIG. 2 would typically be limited by the number of whitespacechannels the home gateway interface 210 can simultaneously support. Foreach television signal receiver 230, 250, 270, the home gatewayinterface 110 would require ability to transmit over a whitespacechannel to the television receiver. This could be accomplished byplug-in modules for each receiver in the home gateway interface 210system, or set top boxes for each display device not capable ofreceiving an RF signal from the home gateway interface 210. The set topbox or plug in module typically would support graphics and audiorequirements for one display device, however, a set top box could beconfigured to share some processing with multiple television interfaces.These multiple device set top boxes may comprise capabilities such asvideo transport stream processing, graphics rendering and videocompression and encoding, agile ATSC modulator.

The home gateway interface 210 could receive content from a hard drive220 or like memory device, an antenna 212 for receiving broadcastsignals such as ATSC broadcasts or satellite signals, or through localarea network connections IN1 or internet connections IN2. As with thesystem of FIG. 1, the gateway network interface 210 could broadcastmodulated video or audio programs over one or more unused white spacechannels via an ATSC transmit antenna 214 to the television signalreceivers and transmit data and receive commands from the remotecontrols 240, 260, 280 via another RF antenna 216.

Each remote control 240, 260, 280 would be associated with a singletelevision signal receiver 230, 250, 270 since the home gatewayinterface 210 would need to establish a relationship between aparticular remote control 240, 260, 280 and a particular televisionreceiver 230, 250, 270 so that the programming modulated on a particularwhite space channel is received and decoded by the intended televisionreceiver 230, 250, 270. For example, if one remote control 240 waspaired with one television signal receiver 230, when the user wished tochange programming, an RF signal is sent from the remote control 240 tothe home gateway interface 210 via the RF antenna 216. The home gatewayinterface 210 processes the request and changes the content broadcast onthe white space channel being received by the television signal receiver230. In this example, the television signal receiver would not changethe RF channel tuned, much in the same way a television signal receiverconnected to a video cassette recorder could always tune channel 3 whilethe received broadcast is being changed via the video cassetterecorder's tuner. However, if a user then moved the remote control 240to a different television signal receiver 270 and tried to change theprogram being viewed on that television signal receiver 270, the homegateway interface would not know the user had moved and wouldsubsequently change the display of the television signal receiver 230originally paired with that particular remote control 240. This problemcould be overcome by placing a device one or near each television whichwould send an IR or RF signal to the remote control when the remotecontrol comes within range of the television signal receiver 270. Inresponse to receiving this signal, the remote control 240 would update anew pairing to the home gateway interface 210 so that the home gatewayinterface 210 would change the programming on the correct white spacechannel in response to a user command. Additionally, the remote controlcould transmit an RF signal to receivers located at each of thetelevision signal receiver 230, 250, 270 and use responses from thetelevision signal receivers 230, 250, 270, or attached devices, todetermine a distance from each television signal receiver 230, 250, 270.The remote control 240 could then use this information to determinewhich television signal receiver 230, 250, 270 is closest to the remotecontrol 240 and therefore most likely being viewed by the user, andtransmit this relationship to the home gateway interface 210 toestablish the correct pairing. This same operation could be performedusing an IR transmitter and receiver in the remote control 240 and thetelevision signal receiver 230, 250, 270. This would ensure a line ofsite connection between the remote control 230 and the television signalreceiver 230, 250, 270 to aid in establishing a correct pairing.Therefore, according to this exemplary embodiment, when a user traveledaround a residence with a remote control 240 into rooms with televisionsignal receivers 230, 250, 270 operating with the home gateway interface210, the home gateway interface 210 and the remote control 240 wouldautomatically establish a pairing between the television signal receiver230, 250, 270 most likely being viewed by the user and the remotecontrol 240 being carried by the user. This pairing could also be madein response to a button push or the like on the remote control 240 bythe user when the user when a new pairing is to be made.

The remote control 240 can serve as a pointer for the gateway interfaceusing television receivers. While not necessary, use of a pointer typefunction will facilitate the user interface that people have come toexpect of computer systems today, such as a mouse or trackball device.This the movement of the pointer can be achieved through directionbutton pushes on the remote control, motion sensors within the remotewhich translate movement of the remote control into directional movementof the pointer. A wireless keyboard could also be used to interface thehome gateway. A computer based terminal could use a remote, or any humaninterface device supported on the computer.

During setup of the system, the remote control 240, 260, 280 would beaffiliated or paired with a display device. A method for establishingthis pairing could use different whitespace channels allocated todifferent transmitters at the gateway, which in turn, are to be receivedby different television signal receivers 230, 250, 270. First, the homegateway interface 210 uses spectrum sensing and/or geo-location databaseto find available whitespace channels. The home gateway interface 210assigns channels to its transmitters, and provides a unique ID numberfor each channel. When the user surfs through the TV channels and findsa home gateway interface 210 welcome screen, he enters a key sequencewith the welcome screen ID number into the remote control 240, 260, 280.This tells the home gateway interface 210 which whitespace channel isaffiliated with each remote control device 240, 260, 280. The homegateway interface 210 indicates to the remote control 240, 260, 280 thatthis is the channel that will be used when the home gateway interface210 access button is pressed. The user can now access the contentavailable from the home gateway interface 210, since the televisionsignal receiver 230, 250, 270 has become a display wirelessly connectedto the home gateway interface 210. The remote control 240, 260, 280 mayhave a means of selecting “gateway mode,” where the remote control 240,260, 280 will tell the television signal receiver 230, 250, 270 whichchannel to use received via RF interface to home gateway interface 210,and the remote control 240, 260, 280 will access content on the homegateway interface 210 via the RF interface, while keeping the televisionsignal receiver 230, 250, 270 tuned to the correct whitespace channel.This mode control is typically accomplished as a row of device buttonsshowing what the remote control 240, 260, 280 will control—for example,satellite, cable, DVD, gateway, etc. Using this interface, the user cansend content to multiple television signal receivers tuned to the samewhitespace channel, and control all of them with the remote control 240,260, 280. Using other modes than gateway mode, the remote control 240,260, 280 can perform traditional remote control functions. In gatewaymode, the remote control 240, 260, 280 sends RF commands back to thegateway to control the content on the affiliated whitespace channel. Ingateway mode the remote control 240, 260, 280 will change TV parameters,such as brightness, contrast, volume, etc., but the channel will bechanged only if directed by the home gateway interface 210. The channelchange would be initiated because of an incumbent user appearing in thechannel, or because the user requested a different whitespace channelbecause of reception difficulty.

Turning to FIG. 3, a flow chart of an exemplary method of initializing awhite space home gateway interface according to the present invention isshown. The method of FIG. 3 shows the initialization sequence 300 for ahome gateway interface 210 of FIG. 2 used in a ATSC broadcastenvironment. When power is applied to the home gateway interface, or asimilar initialization event 302, the home gateway interface tunes afirst ATSC channel 305. The home gateway interface searches 310 for thepresence of an ATSC signal. If a signal is present 315, the home gatewayinterface advances to the next ATSC channel 325. If the signal is notpresent 315, the home gateway interface adds the ATSC channel to a listof available white space channels 320. The home gateway interface thenadvances to the next ATSC channel 325. The home gateway interface thendetermines if all channels have been scanned. If not, the home gatewayinterface returns to step 305 and proceeds for all of the remaining ATSCchannels. If the home gateway interface determines that all of the ATSCchannels have been scanned 330, the home gateway interface proceeds toallocate white space channels to available hardware transmitters 335.After the white space channels have been allocated, the home gatewayinterface then transmits a welcome screen ID on available transmitters335. The home gateway interface then waits for feedback from remotecontrols 345. The user may then provide feedback on the transmissionreception. An example of this feedback might be entering a numeric codeor the like depicted on the welcome screen. The remote transmits thiscode to the home gateway interface along with a remote controlidentifier. Once feedback has been received from a remote control, theremote control identifier is associated with the white space channelshaving that numeric code depicted on the welcome screen and theassociated is stored in the white space channel list 350. Once a remotecontrol is associated with the white space channel, the home gatewayinterface starts normal operation by transmitting a gateway welcome menuon each transmitter associated with a remote 355.

Turning to FIG. 4, a flow chart of an exemplary method of mitigatinginterference in a home gateway interface according to the presentinvention is shown. The method of FIG. 4 shows an interferencemitigation routine 400 for the home gateway system of FIG. 2. In theevent of interference issues on a given whitespace channel, the user cantrigger a frequency change by pressing a key sequence to enable awhitespace channel change. Since the gateway has access to the remoteand the transmitter, it can change frequencies at the suggestion of theuser, or automatically if interference is detected.

The home gateway interface monitors for transmissions from the remotecontrol. When a code indicating that the interference mitigation key hasbeen pressed 405, the home gateway interface checks the white space listfor the next available white space channel 410. The home gatewayinterface then changes the transmit frequency of the RF transmitter 415to that of the next available white space channel. The home gatewayinterface then transmits data indicating the new white space channel tothe remote control 430. The remote control then changes the channel ofthe television signal receiver 435 locally in response to receiving thisdata. The home gateway interface then updates the white space list withthe new allocation 440. The home gateway interface then returns tomonitoring for data from the remote controls.

Turning to FIG. 5, a block diagram of a dual frequency white spacesystem embodying aspects of the present invention is shown. The systemof FIG. 5 illustrates a system 500 with parallel interruptedtransmissions to permit quiet times for microphone detection. An issuethat may influence the design of the home gateway interface is thatwireless microphone detection may need to be performed frequently, onthe order of every few seconds. This could be a challenge for thecontinuous single channel links suggested in the previous examples,since the transmitter must be silenced to detect signals 20 dB below thenoise floor. To address this problem, a dual transmitter home gatewayinterface and a dual-tuner receiver can ping-pong between two whitespace channels, permitting a dedicated streaming channel to be realizedacross two ATSC channels. Microphone sensing can occur while thealternating channel is not transmitting. This would enable robust highquality of service streaming delivery to a receiver designed to handlethe ping-pong transmission.

The home gateway interface 510 utilizing the parallel transmissionmethod would transmit the requested signal on two available white spacechannels. Each of the channels would have periodic outages at differenttimes to attempt to detect new transmitters in that frequency, such aswireless microphones. The home gateway interface could receive commandsand data from the alternating channel receiver 520 via local areanetwork, either hardwired or wireless, or through a remote control.

The alternating channel receiver 520 comprises two tuners, each of whichare tuned to one of the white space channels being transmitted on by thehome gateway interface. Each tuner may be coupled with its owndemodulator such that each channel is demodulated and a processor withinthe television receiver can easily switch between signals in the eventof a periodic outage for detecting new transmitters. Alternately, thesystem may be equipped with a single demodulator and a multiplexer forswitching the outputs of the tuners to the input of the demodulatorduring overlap periods when both channels are transmitting.

In another exemplary embodiment, only single tuner is required at thealternating channel receiver 520. The transmitter at the home gatewayinterface 510 periodically switches to different whitespace channels, orping-pongs between two whitespace channels, to allow the home gatewayinterface 510 to sense the wireless microphone in the previous operatingchannel. The home gateway interface 510 informs the alternating channelreceiver 520 of the channel change either through the current whitespace channel or through a second RF link such as WLAN. If thetransmitter is streaming audio/video contents using the whitespacechannels, there may be transmission interruption during the channelchange. The second RF link can be used to send additional data tocompensate the transmission interruption such that the streaming qualityis maintained. Alternately, signal buffering can be used to compensatefor the transmission interruption.

The second two-way RF link, such as WLAN, at the alternating channelreceiver 520 can also be used to provide reliable data delivery: data ordata file are delivered through ATSC transmitters (or DVB T/H, QAMtransmitters) using white space channels. Due to the broadcast nature ofthe transmission and lack of acknowledgement of reception error in theATSC transmission, the reliable data delivery cannot be ensured. Thesecond RF link can be used to provide the or positive or negativeacknowledgment of the data reception such that those data with receptionerror can be re-transmitted in ATSC transmission or transmitted in thesecond RF link if it has sufficient capacity. In another embodiment, theFEC coded data of those data with reception error can be transmitted inATSC transmission or the second RF link to allow the recover the data inerror.

Turning to FIG. 6, the parallel transmission of data 600 over a dualfrequency white space system embodying aspects of the present inventionis shown. Channel A indicates the transmission of data over time withperiodic outages for microphone detection slots as shown. Channel Bindicates a similar transmission of data over time at a differentfrequency with microphone detection slots staggered in time with themicrophone detection slots of Channel a. The overlap of transmit slotsbetween Channel A and channel B can used to alternate which channel isprocessed with minimal signal loss and by implementing the previouslydescribed methods.

While the present invention has been described in terms of a specificembodiment, it will be appreciated that modifications may be made whichwill fall within the scope of the invention. For example, variousprocessing steps may be implemented separately or combined, and may beimplemented in general purpose or dedicated data processing hardware.

The invention claimed is:
 1. An apparatus comprising: a firsttransmitter configured to transmit an audio/video program at a firstfrequency; a second transmitter configured to transmit said audio/videoprogram at a second frequency; a detector configured to detect externaltransmission, by a transmitter external to the apparatus, at said firstfrequency and said second frequency; and wherein said detector isoperative to detect said external transmission during a first timeperiod at said first frequency when said first transmitter stopstransmitting said audio/video program and said second transmitter istransmitting said audio/video program at said second frequency, and todetect said external transmission during a second time period at saidsecond frequency when said second transmitter stops transmitting saidaudio/video program and said first transmitter is transmitting saidaudio/video program at said first frequency, wherein said firstfrequency and said second frequency are white space channels, furtherwherein said first time period and said second time period occur atdifferent times, and further wherein transmission over said firstfrequency and transmission over said second frequency provide paralleluninterrupted transmission of said audio/video program.
 2. The apparatusof claim 1 wherein said external transmitter is a wireless microphone.3. The apparatus of claim 1 wherein said first frequency and said secondfrequency are white space channels.
 4. The apparatus of claim 3 whereinsaid detector detects said white space channels before attempting todetect said external transmitter.
 5. The apparatus of claim 1 whereinsaid first time period and said second time period do not overlap intime.
 6. The apparatus of claim 1 wherein said first transmitter andsaid second transmitter stop transmitting periodically.
 7. The apparatusof claim 1 wherein a single baseband signal is constructed from theaudio/video program transmitted at said first frequency and theaudio/video program transmitted at said second frequency.
 8. A methodperformed by an apparatus comprising: transmitting, by a firsttransmitter, an audio/video program at a first frequency; transmitting,by a second transmitter, said audio/video program at a second frequency;detecting, by a detector, an external transmission by a transmitterexternal to the apparatus, at said first frequency and at said secondfrequency; and wherein said detecting attempts to detect said externaltransmission during a first time period at said first frequency whensaid first transmitter stops transmitting said audio/video program andsaid second transmitter is transmitting said audio/video program at saidsecond frequency, and to detect said external transmission during asecond time period at said second frequency when said second transmitterstops transmitting said audio/video program and said first transmitteris transmitting said audio/video program at said first frequency,wherein said first frequency and said second frequency are white spacechannels, further wherein said first time period and said second timeperiod occur at different times, and further wherein transmission oversaid first frequency and transmission over said second frequency provideparallel uninterrupted transmission of said audio/video program.
 9. Themethod of claim 8 wherein said external transmitter is a wirelessmicrophone transmitting at one of said first frequency and said secondfrequency.
 10. The method of claim 8 further comprising detecting saidfirst white space channel and said second white space channel beforeattempting to detect said external transmitter.
 11. The method of claim8 wherein said transmitting at said first frequency and stopping saidtransmitting at said first frequency by said first transmitter areperformed periodically.
 12. The method of claim 8 whereinsaid-transmitting at said second frequency and stopping saidtransmitting at said second frequency by said second transmitter areperformed periodically.
 13. The method of claim 8 wherein a singlebaseband signal is constructed from the audio/video program transmittedat said first frequency and the audio/video program transmitted at saidsecond frequency.